Process for producing acetylene



Oct. 26, 1954v P, w @ARBO v 2,692,901

PROCESS FOR PRODUCING ACETYLENE Filed NOV. 15, 1951 L Awbz/c T @A s NATI/PA L 61,45'

INVEN TOR. PAM/J W GA m90 BY .Y ZTQRNEYS Patented Oct. 26, 1954 PROCESS FOR PRODUCING ACETYLENE Paul W. Garbo, Freeport, N. Y., assignor to Hydrocarbon Research, Inc., New York, N. Y., a corporation of New Jersey Application November 15, 1951, Serial No.` 256,576

Claims. (Cl. 260-679) This invention relates to an improvement in the production of acetylene by the partial combustion of a hydrocarbon. More particularly, it discloses a novel method for rapidly cooling acetylene-containing gas produced by partial combustion of a hydrocarbon gas.

Acetylene is produced by the high temperatureshort contact time partial combustion of a hydrocarbon such as methane; generally temperatures between 2500 and 3000" F. and contact times between 0.001 and 0.1 second are suitable for the production of acetylene by the partial combustion of a hydrocarbon. It is known that it is necessary to cool the acetylene-containing product gas as quickly as possible after the partial combustion in order to minimize decomposition or other undesired reaction of the thermally unstable acetylene. Various procedures have been suggested to accomplish the quenching of the acetylene-containing product gas. One of the most eii'icient procedures for quenching the product gas involves contact of the product gas with cool, nely divided particles of thermally absorptive materials such as alumina, silica, metallic aluminum, etc. The introduction of nely divided particles of a heat carrier into the acetylene-containing product stream is an eincient means of quenching because of the heat capacity and heat transmission properties of the particulate solid. The process of the subject invention is substantially more eliicient than previously known methods for cooling acetylene-containing gas produced by partial combustion of a hydrocarbon.

In accordance with the process of this invention, quenching of acetylene-containing gas produced by the partial combustion of a hydrocarbon, preferably a gaseous hydrocarbon such as methane, is effected by the introduction of nely divided particles of a higher iron oxide (such as FezOa and Fe304) into the gas produced by partial combustion of the hydrocarbon generally at a temperature between 2500o to 3000 F. and at a contact time between 0.001 and 0.1 second. Contact of the hot product gas with iinely divided particles of the higher iron oxide which are at a relatively low temperature, say not more than 600 F., eiects rapid and eiiicient cooling of the product gas to a temperature below about 800 F.; ordinarily, the product gas is cooled to a temperature between about 650 and '750 F. by the introduction of the higher iron oxide therein. The superiority of the process of this invention for quenching acetylene-containing product gas is attributable to the fact that the conventional sensible-heat cooling and heat exchange effected by a iinely divided solid are supplemented materially by the endothermic reduction of the higher iron oxide to a lower oxide (not lower than FeO). 'I'he solid quench material may be entrained in the product gas and readily separated therefrom by conventional means such as cyclone separators.

A signieant advantage of the process of the invention is that the concentration of the acetylene in the cooled gas is substantially increased as a consequence of the reduction of the higher iron oxide by the hydrogen and carbon monoxide present in the product gas. The acetylene content on a dry basis of the gas quenched by the process of this invention may be as high as 12 to 14 per cent by volume which compares very favorably With 8 to 9 per cent acetylene content of the same gas quenched by conventional means.

The lower iron oxide produced during the quenching of acetylene-containing gas may be reoxidized with air or oxygen to form the higher oxide of iron and then recycled, after cooling to a temperature below about 600 F., to the quench zone. Reoxidation of the used quench material to a higher iron oxide is an exothermic reaction and the heat liberated therein can be used in the heating of the methane or other hydrocarbon and oxygen streams prior to their combination for production oi acetylene by partial combustion. The recycle operation involving oxidation of the quench material and recycle of iron oxide in a higher state of oxidation to the quenching zone is a self-contained unitary process which provides the most efficient means yet devised for the quenching of a hot acetylene-containing gas.

While ferrie oxide (FezOa) and magnetite (FegOr-ferrosoferric oxide) may be employed as the higher iron oxide in the process of the invention, magnetite is the preferred material. The qunching capacity of magnetite is approximately twice that of ferrie oxide. In the further description of the invention, magnetite will be employed as the quench material.

The partial combustion process for the production of acetylene is ordinarily carried out at atmospheric pressure. The ratio of atoms of oxygen to atoms of carbon, termed the O/C ratio, in the feed gases, is usually in the range of 1.1 to 1.3. In the typical operation, the product of the partial combustion comprises on a volume basis (all moisture having been removed) approximately 8 per cent acetylene, 25 per cent carbon monoxide, 55 per cent hydrogen, 5 per cent carbon dioxide and 5 per cent unconverted methane.

The partial combustion product gas issuing from the reaction zone desirably at a temperature of approximately 2800 F. is immediately contacted with magnetite particles; generally the particle sizes fall predominantly in the range of 100 to 200 mesh. The magnetite particles are usually introduced into the quench zone at a temperature between 450 and 600F.

The temperature of the acetylene-containing gas is quickly dropped to below 800 F. by contact with the cool particles of magnetite. The cool-.- ing eifect of the magnetite particles is principally attributable to two factors, namely, ythe absorption of sensible heat by the solid particles and the endothermic reductionxoi magnetite to ferrous oxide by the hydrogen present in the acetylene-containing product gas. In a fraction of a second, ordinarily less than 0.1 second, the product gas is cooled to a temperature in the range of about 650 to '750 F. by the process of the invention.

Quenching of the product gas is` generally effected bythe use of 0.2 to 2.0 pounds of iron oxide per cubic oot of product gasv issuing from the ccmbustionzone. In most cases, not more than` 1.0pound of iron oxide per cubic foot of product gas will suffice.

The solid particles which have been partly reduced are readily separated-from the cooledproduct gas by conventional means for separating solids from gases. In the preferred modication of the invention involvingoxidation of the separated, partly reduced heat carrier to a higher iron oxide andits recycle to thevquenching zone, the oxidation may be eected with air or oxygen at temperatures in the range of 800 to 1200 E. Steam may be added during the air or oxygen oxidation. Theferric oxide or magnetite formed by the oxidationis cooled toa temperature below about 6.005v Rand recycled to the quench zone.

In theaccompanying drawingthere is diagrammatically illustrated the process-of this invention forA quenching acetylene-containing product gas employing magnetite as the quench material.

Natural gas which` has beenV preheated to a temperature of about 1000. F. is introduced through a pipe Il into4 aA burner` 2 which effects intimate mixing of the-natural gas with oxygen which has been preheated to a temperature of labout 400 If. and which is introduced into the burner 2 through a pipe 3. The O/C ratio of the mixture of natural gas. and oxygen` introduced into the burner 21 is'inV the. range of 1.1 to;` 1.3. In the combustionzone I-.natural gas andoxygen are reacted at a temperature of about 28,00a F., at atmospheric pressure and at a contact time preferably inthe range of' 0.001 `to0.01 second to yield a product gas comprisingapproximately 8 per cent by volume (dry basislof acetylene.

The product gas at reaction temperature issues from the combustion zone @through the constrictecl passage 5 into a quench zone 6. In the quench zone 6 the product gas is contacted with powdered magnetite of predominantly 100 to 200.1nesh particle size which at a temperature of about 600 F. is introduced: through the entry ducts 8. and 0 into the quench zone `Ii. Contact of4 the hot product gas with the coolpowdered magnetite results in the cooling of the product gas to a temperature ofy about 650 to 750 F. inlessI thanA 0.1 second.

The particulate solid which is partly converted to ferrous oxide is entrained in the product gas` and is carried out of the quenching zone' .throughz the conduit I0 which. leads to a gas-solid separator I2. The solid particles are separated from the product gas in the separator I2 and are removed therefrom through a pipe I4.

The product gas removed from the separator I2 through a pipe I5 is sent to a recovery system wherein the acetylene is separated from the other components of the gas. The recovery of acetylene from theproduct gas is not a part of the process of this invention and there-are a number of well-known procedures for effecting separation of acetylene from the CO, I-Iz, CO2 and CH4 components of theA product gas.

The partly reduced particles separated from theproduct gas are introduced through the pipe UI into a roaster Il wherein they are oxidized to ferric oxide and magnetite with air, desirably at atemperature of 800 to 1200 F. Air which has been preheated to a temperature of about 500 F. is introduced through a pipe 20, a blower 2l and a pipe 23 into the roaster I'I. The heat liberated during the exothermic oxidation ofA ferrous oxide `to ferric oxide and magnetite canbe used for preheating the air'introduced into the roaster or the natural gas and oxygen which are partially burned to yield acetylene. The waste gas from which heat can be recovered issues from the roaster I'I through a pipe 25.

The higher oxide of iron is withdrawn from the roaster IV'I through a pipe 2'I,.cooledv in exchanger 28\ to a temperature of about 600 F., and is then passed through pipes 29 and 30 to the entry ducts 8 and 9, and thence into quench zone Ii.

The process of the invention is illustrated inzthe following vexarnplewherein the acetylene-containing product gas is cooled by contact, withmagnetite.

10,000. cubic feet .ofznatural gas and,f3,200y cubic feet of .oxygen (approximately 96% by Volume purity) measured at standardY conditions are charged hourly to a reaction zonewherein. they undergo partial` combustion at a temperature of about 2800 F; to,form 23,800. cubicfeet of gas having the following approximatevolume composition:

Per cent Hydrogen 38 Water v25 Carbonl monoxide 21 Acetylene 6 Methane 3;5 Carbon dioxide 2.8 Others 3.7

This gas is cooled-to.700 F. by the use of 12,000 lbs. ofk magnetite vintroduced hourly. intov the quenchv zone. The-magnetite is partly reduced to ferrous oxide during the` quenching operation. While on adry basis the` acetylene content `ofthe, product gas.is18%by volume, .after theduenching operationbecause. ofl the loss of'hydrogen. in the I partial. reduction ofi the magnetite the quenched gas .on a drybasis has .an acetylene con.- tentof 12.3% by Volume.

Thus, it will be observed that quenchingiof'the product gas with magnetite not only.. eifectssuperior cooling of the product gas but alsoeffects a substantial'increase in the acetyleneV concentra'- tion of the product; gastherebyv facilitating; the: subsequent isolation of acetylene fromthe product gas.

Itis apparentthat the process of this invention providesV an efficient, simple process for. quenchingy acetylene-containing` gas produced by the` partialf combustion .ofi al hydrocarbon. The

cyclic operation whereby the ferrous oxide produced during the quenching is oxidized and returned to the quenching zone requires a minimum of steps.

Obviously, many modifications and variations of the invention as hereinabove set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. In the production of acetylene by partial combustion of a hydrocarbon with oxygen at a temperature above about 2,500 F., the improvement which comprises quenching the acetylenecontaining product gas at said temperature by contact with particles consisting of iron oxides predominantly in a higher state of oxidation than ferrous oxide in an amount in the range of from 0.2 to 2 pounds of said solid particles per cubic foot of said product gas, said solid particles having a temperature of not more than about 600 F. and a size range predominantly in the range of 100 to 200 mesh whereby the temperature of said product gas is reduced to a temperature below about 800 F. with concomitant partial reduction of said higher oxide to a lower oxide not lower than ferrous o xide.

2. The method according to claim 1 wherein said solid particles introduced into contact with said product gas have a temperature of not less than about 450 F.

3. The method according to claim 1 wherein said higher oxide of iron is predominantly magnetite and the lower oxide is ferrous oxide.

4. In the production of acetylene by partial combustion of a hydrocarbon with oxygen at a temperature above about 2.500 F., the improvement which comprises quenching the acetylenecontaining product gas at said temperature by contact with particles consisting of iron oxides predominantly in a higher state of oxidation than ferrous oxide in an amount in the range of from 0.2 to 2 pounds of said solid particles per cubic foot of said product gas, said solid particles having a temperature of not more than about 600 F. and a size range predominantly inthe range of to 200 mesh thereby simultaneously cooling said product gas to a temperature below about 800 F. and reducing said higher oxide of iron to a lower oxide not lower than ferrous oxide, separating solid particles comprising ferrous oxide from the quenched product gas, re-oxidizing said ferrous oxide in said separated particles to a higher oxide of iron, and thereafter returning said particles to said quenching step.

5. The method according to claim 4 wherein said solid particles introduced into contact with said product gas have a temperature of not less than about 450 F.

References Cited in the flle of this patent UNITED STATES PATENTS Number Name Date 2,422,501 Roetheli June 17, 1947 2,443,210 Upham June 15, 1948 2,541,693 Frevel et al. Fe'b. 13, 1951 

1. IN THE PRODUCTION OF ACETYLENE BY PARTIAL COMBUSTION OF A HYDROCARBON WITH OXYGEN AT A TEMPERATURE ABOVE ABOUT 2,500* F., THE IMPROVEMENT WHICH COMPRISES QUENCHING THE ACETYLENECONTAINING PRODUCT GAS AT SAID TEMPERATURE BY CONTACT WITH PARTICLES CONSISTING OF IRON OXIDES PREDOMINANTLY IN A HIGHER STATE OF OXIDATION THAN FERROUS OXIDE IN AN AMOUNT IN THE RANGE OF FROM 0.2 TO 2 POUNDS OF SAID SOLID PARTICLES PER CUBIC FOOT OF SAID PRODUCT GAS, SAID SOLID PARTICLES HAVING A TEMPERATURE OF NOT MORE THAN ABOUT 600* F. AND A SIZE RANGE PREDOMINANTLY IN THE RANGE OF 100 TO 200 MESH WHEREBY THE TEMPERATURE OF SAID PRODUCT GAS IS REDUCED TO A TEMPERATURE BELOW ABOUT 800* F. WITH CONCOMITANT PARTIAL REDUCTION OF SAID HIGHER OXIDE TO A LOWER OXIDE NOT LOWER THAN FERROUS OXIDE. 